DESCRIPTION The aims of the parent project are the isolation and characterization in mouse of novel genes mapping to the Down Syndrome Critical Region of human chromosome 21q22.2. During the last 3 years, however, it has become clear that genes mapping outside this small region are also of importance to the Down Syndrome phenotype and that studies should be expanded to investigate genes within other regions of 21q. The aims of the FIRCA are to isolate and analyze complete cDNAs for eight such novel 21q genes; to isolate the corresponding genomic clones from mouse; and to identify and analyze control regions for these genes from both human and mouse. These studies will aid in the determination of the function of these genes, and thus their potential relevance to Down Syndrome, and also will provide resources for possible future construction of transgenic mice for verification of phenotype. All genes chosen for study under the FIRCA map outside the Down Syndrome Critical Region are expressed in brain, and all have interesting homologies or expression patterns. Dr. Gardiner will supply Dr. Rynditch with the human and mouse chromosome 21 cDNA fragments from each of the 8 genes, together with current available sequences, primers, and expression data. Dr. Rynditch will use 5' and 3' RACE techniques to isolate and clone complete transcripts for each gene. Dr. Rynditch will isolate genomic clones for each human and mouse gene and define 5-10 kb regions 5' and 3' of the coding sequences for each. Sequencing of cDNAs and genomic regions will be carried out by both manual and automated methods. In addition, Dr. Rynditch will also define the intron/exon structure of 2 genes located within the AML1 gene and investigate their relationship to that of the AML1 gene structure. The FIRCA will allow expansion of the parent grant into the new areas of RACE technologies and analysis of gene control regions, and will provide important new information regarding novel genes relevant to the Down Syndrome phenotype.